Method, Apparatus, and System for Efficient Rate Control in Audio Encoding

1. A method comprising: receiving audio samples representing an input audio signal; transforming the input audio samples into a vector of spectral values in a frequency domain; and determining a value of a quantizing parameter, including: determining the value of the quantizing parameter, such that a maximum quantized value does not exceed a maximum index of one or more corresponding codebooks; and determining the value of the quantizing parameter based on a modified Newtonian search process, the determined value of the quantizing parameter being used to quantize the respective vector of spectral values to generate a vector of quantized values such that a total number of bits used for encoding the vector of quantized values does not exceed a maximum number of bits available for encoding the vector of the quantized values.

2. The method of claim 1 wherein the one or more codebooks are Huffman code tables.

3. The method of claim 1 wherein the value of the quantizing parameter is determined according to the following formula: global_gain ≥ ⌈ A · log 2 ⁡ ( MAX ⁢  x r ⁡ ( i )  [ B - C ] D ) ⌉ wherein global_gain corresponds to the value of the quantizing parameter, A corresponds to a first constant, xr(i) corresponds to an original spectral value for frequency line i, B corresponds to a second constant representing a maximum quantized spectral value, C corresponds to a third constant, and D corresponds to a fourth constant.

4. The method of claim 1 including: computing a first estimate and a second estimate for the quantizing parameter; and performing a set of operations iteratively until a predetermined number of iterations is reached, including: deriving a new estimate for the quantizing parameter based on the previous estimates for the quantizing parameter.

5. The method of claim 4 wherein deriving the new estimate includes: calculating a line tangent to a function representing the total number of bits used based on the previous estimates; and calculating the new estimate based on an intercept between the line tangent calculated and a line representing the maximum number of bits available.

6. The method of claim 4 wherein performing the set of operations further including: determining whether the total number of bits based upon the new estimate exceeds the maximum number of bits available; if the total number of bits based upon the new estimate exceeds the maximum number of bits available, increasing the new estimate by a first factor; and if the total number of bits based upon the new estimate does not exceed the maximum number of bits available, decreasing the new estimate by a second factor.

7. The method of claim 6 wherein the first factor and second factor are integer values.

8. The method of claim 4 wherein the value of the quantizing parameter determined with respect to one block of spectral values is stored in memory and used as an initial estimate for a next block of spectral values.

9. An apparatus comprising: logic to receive input audio samples representing corresponding input audio signals; logic to transform the input audio samples into a vector of spectral values in a frequency domain; and logic to determine a value of a quantizing parameter, including: logic to determine the value of the quantizing parameter such that a maximum quantized value does not exceed a maximum index of one or more corresponding codebooks; and logic to determine the value of the quantizing parameter based on a modified Newtonian search process, the determined value of the quantizing parameter being used to quantize the respective vector of spectral values to generate a vector of quantized values such that a total number of bits used for encoding the vector of quantized values does not exceed a maximum number of bits available for encoding the vector of the quantized values.

10. The apparatus of claim 9 wherein the value of the quantizing parameter is determined according to the following formula: global_gain ≥ ⌈ A · log 2 ⁡ ( MAX ⁢  x r ⁡ ( i )  [ B - C ] D ) ⌉ wherein global_gain corresponds to the value of the quantizing parameter, A corresponds to a first constant, xr(i) corresponds to an original spectral value for frequency line i, B corresponds to a second constant representing a maximum quantized spectral value, C corresponds to a third constant, and D corresponds to a fourth constant.

11. The apparatus of claim 9 including: logic to compute a first estimate and a second estimate for the quantizing parameter; and logic to perform a set of operations iteratively until a predetermined number of iterations is reached, including: logic to derive a new estimate for the quantizing parameter based on the previous estimates for the quantizing parameter.

12. The apparatus of claim 11 wherein logic to derive the new estimate including: logic to calculate a line tangent to a function representing the total number of bits used based on the previous estimates; and logic to calculate the new estimate based on an intercept between the line tangent calculated and a line representing the maximum number of bits available.

13. The apparatus of claim 12 wherein logic to perform the set of operations further including: logic to determine whether the total number of bits based upon the new estimate exceeds the maximum number of bits available; logic to increase the new estimate by a first integer if the total number of bits based upon the new estimate exceeds the maximum number of bits available; and logic to decrease the new estimate by a second integer if the total number of bits based upon the new estimate does not exceed the maximum number of bits available.

14. A system comprising: a transformation unit to transform input audio samples representing corresponding audio signals into a vector of spectral values in a frequency domain; a psychoacoustic modeling unit to analyze the input audio samples and generate a frequency mask; and a bit allocator and quantizer unit coupled to the transformation unit and the psychoacoustic unit, the bit allocator and quantizer unit including: logic to determine a value of a quantizing parameter, including: logic to determine the value of the quantizing parameter such that a maximum quantized value does not exceed a maximum index of one or more corresponding codebooks; and logic to determine the value of the quantizing parameter based on a modified Newtonian search process, the determined value of the quantizing parameter being used to quantize the respective vector of spectral values to generate a vector of quantized values such that a total number of bits used for encoding the vector of quantized values does not exceed a maximum number of bits available for encoding the vector of the quantized values.

15. The system of claim 14 wherein logic to determine the value of the quantizing parameter includes: logic to compute the value of the quantizing parameter such that a maximum quantized value does not exceed a maximum index of one or more corresponding codebooks, based upon the following formula: global_gain ≥ ⌈ A · log 2 ⁡ ( MAX ⁢  x r ⁡ ( i )  [ B - C ] D ) ⌉ wherein global_gain corresponds to the value of the quantizing parameter, A corresponds to a first constant, xr(i) corresponds to an original spectral value for frequency line i, B corresponds to a second constant representing a maximum quantized spectral value, C corresponds to a third constant, and D corresponds to a fourth constant.

16. The system of claim 14 including: logic to compute a first estimate and a second estimate for the quantizing parameter; and logic to perform a set of operations iteratively until a predetermined number of iterations is reached, including: logic to derive a new estimate for the quantizing parameter based on the previous estimates for the quantizing parameter.

17. The system of claim 16 wherein logic to derive the new estimate including: logic to calculate a line tangent to a function representing the total number of bits used based on the previous estimates; and logic to calculate the new estimate based on an intercept between the line tangent calculated and a line representing the maximum number of bits available.

18. The system of claim 17 wherein logic to perform the set of operations further including: logic to determine whether the total number of bits based upon the new estimate exceeds the maximum number of bits available; logic to increase the new estimate by a first integer if the total number of bits based upon the new estimate exceeds the maximum number of bits available; and logic to decrease the new estimate by a second integer if the total number of bits based upon the new estimate does not exceed the maximum number of bits available.

19. A machine-readable medium comprising instructions which, when executed by a machine, cause the machine to perform operations including: receiving audio samples representing an input audio signal; transforming the input audio samples into a vector of spectral values in a frequency domain; and determining a value of a quantizing parameter, including: determining the value of the quantizing parameter such that a maximum quantized value does not exceed a maximum index of one or more corresponding codebooks; and determining the value of the quantizing parameter based on a modified Newtonian search process, the determined value of the quantizing parameter being used to quantize the respective vector of spectral values to generate a vector of quantized values such that a total number of bits used for encoding the vector of quantized values does not exceed a maximum number of bits available for encoding the vector of the quantized values.

20. The machine-readable medium of claim 19 wherein determining the value of the quantizing parameter includes: determining the value of the quantizing parameter such that a maximum quantized value does not exceed a maximum index of one or more corresponding codebooks according to the following formula: global_gain ≥ ⌈ A · log 2 ⁡ ( MAX ⁢  x r ⁡ ( i )  [ B - C ] D ) ⌉ wherein global_gain corresponds to the value of the quantizing parameter, A corresponds to a first constant, xr(i) corresponds to an original spectral value for frequency line i, B corresponds to a second constant representing a maximum quantized spectral value, C corresponds to a third constant, and D corresponds to a fourth constant.

21. The machine-readable medium of claim 19 including: computing a first estimate and a second estimate for the quantizing parameter; and performing a set of operations iteratively until a predetermined number of iterations is reached, including: deriving a new estimate for the quantizing parameter based on the previous estimates for the quantizing parameter.

22. The machine-readable medium of claim 21 wherein deriving the new estimate includes: calculating a line tangent to a function representing the total number of bits used based on the previous estimates; and calculating the new estimate based on an intercept between the line tangent calculated and a line representing the maximum number of bits available.

23. The machine-readable medium of claim 22 wherein performing the set of operations further including: determining whether the total number of bits based upon the new estimate exceeds the maximum number of bits available; if the total number of bits based upon the new estimate exceeds the maximum number of bits available, increasing the new estimate by a first factor; and if the total number of bits based upon the new estimate does not exceed the maximum number of bits available, decreasing the new estimate by a second factor.